https://jslhr.pubs.asha.org/article.aspx?articleid=1782688Error Variability in Apraxia of Speech: A Matter of ControversyPurposeError variability has traditionally been considered a hallmark of apraxia of speech (AOS). However, in some of the current AOS literature, relatively invariable error patterns are claimed as a mandatory criterion for a diagnosis of AOS. This paradigm shift has far-reaching consequences for our understanding of the disorder and for ...2012-10-01T00:00:00Supplement: Apraxia of Speech: Concepts and ControversiesAnja Staiger

PurposeError variability has traditionally been considered a hallmark of apraxia of speech (AOS). However, in some of the current AOS literature, relatively invariable error patterns are claimed as a mandatory criterion for a diagnosis of AOS. This paradigm shift has far-reaching consequences for our understanding of the disorder and for its (differential) diagnosis. Against the background of this controversy, the present article aims to further examine error variability in AOS.

MethodFour patients with relatively pure, mild-to-moderate AOS participated in the study. They repeated 8 target words in 2 different phrase contexts, 10 times each. Error analyses were based on phonetic transcription. Error variability was determined using several measures of (a) consistency of error occurrence and (b) consistency of error type.

ResultsAll patients produced highly inconsistent reactions across multiple trials in some of the target words. However, other words were more consistently accurate or inaccurate. Several factors influencing error variability were identified.

ConclusionsBecause this study has disclosed clear indications of variable behavior in AOS, diagnostic guidelines claiming error consistency as a mandatory criterion cannot be maintained. Because error variability is difficult to operationalize, we recommend to no longer use (in)consistency as a strict diagnostic marker of AOS.

Acknowledgments

This article originated from a presentation given at the “Apraxia of Speech: Mechanisms and Symptoms” satellite workshop during the 6th International Conference on Speech Motor Control in Groningen, the Netherlands, June 2011. This study was supported by German Research Council (Deutsche Forschungsgemeinschaft [DFG]) Grant ZI 469/10-3. We thank ReHa-Hilfe e.V. (München, Germany) for their support. Patients were referred from the speech therapy department of the Neurological Clinic Bad Heilbrunn and from the Neuropsychological Practice by W. Fries (München, Germany). We are grateful to the therapists from these departments for their cooperation. We are also grateful to speech therapists from the following clinical institutions for their support: Neuropsychological Clinic, Clinic Bogenhausen, City Hospital München; University Hospital, Groβhadern, München; Neurological Clinic Bad Aibling; and Neurological Clinic Schaufling. We also express our gratitude to all participants.

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